EP0061412A1 - Method and apparatus for the manufacture of synthetic-foam sheets - Google Patents

Abstract

PCT No. PCT/FR82/00056 Sec. 371 Date Nov. 1, 1982 Sec. 102(e) Date Nov. 1, 1982 PCT Filed Mar. 23, 1982 PCT Pub. No. WO82/03357 PCT Pub. Date Oct. 14, 1982.An apparatus for manufacturing continuous webs of polymer foam obtained from a mixture of liquid reagents, wherein the volume of a container is determined to form a zone of retention of the mixture of reagents in liquid phase and wherein the level of this mixture is maintained at a level slightly higher than the plane upon which the mixture in the liquid state flows, so that the primary phase of expansion of the mixture and its further expansion are produced outside the container on a moving surface of the conveyor, which surface is maintained in a substantially horizontal plane. The invention is particularly applicable to the production of webs of supple foam or of panels of rigid foam.

Description

The present invention relates to a method and a device for manufacturing strips of polymer foam and product obtained.

The technical sector of the invention is that of equipment for the implementation of flexible or rigid foam strips.

It is known that in the polyurethane foaming process, two simultaneous reactions occur between on the one hand the isocyanate and the polyol (or polyalcohol) and on the other hand between the isocyanate and the water, which produces the main agent of 'expansion: carbon dioxide. This last reaction, possibly combined with the physical phenomenon of the boiling of an auxiliary swelling agent (methylene chloride or trichlorofluomethane) causes the foam to expand. A porous thermosetting material is thus obtained which can be either flexible or rigid depending on the degree of crosslinking of the palymer.

The currently known continuous casting methods consist, for the most part, in distributing the liquid reactive mixture as uniformly as possible over the width of an inclined conveyor, formed by a bottom and by two side walls which move perpendicular to the liquid distribution. This distribution of a mixture of liquid reactants, which is not very viscous, and of rapid reactivity, implies a retention zone capable of containing the liquid spilled for the time necessary and sufficient for this operation. In this design, the inclination of the conveyor is generally 4 to 6 ° over the length necessary for the expansion of the foam and its gelation: between fifteen and twenty meters. The movement is then made on a horizontal plane to the cross cutting equipment: about fifty meters from the casting point.

The most conventional devices include a casting head animated with a transverse movement back and forth and the reactant retention zone is formed, upstream by the bottom of the conveyor, generally consisting of a sheet of flexible material: sheet of paper or of polyethylene, laterally by continuously scrolling walls made of the same material as that of the bottom and downstream, by the product itself which enters its initial reactive phase called "cream line". It is specified that the expression "cream line" designates the state of the mixture of reactants occurring immediately after the liquid phase - and in which this mixture reaches a high viscosity. preceding the formation of the foam. The viscous product adheres to the bottom support and constitutes, constantly renewed, a barrier to the flow of the liquid mixture along the slope of the conveyor. In order to compensate for the absence of mixing in this state, an obstacle is placed downstream of the casting head at the start of manufacture, the role of which is to retain the liquid mixture at start-up.

On this principle, there is a process described in French patent 1,579,795 according to which a transverse element of a determined profile is placed under the flexible support to impart an upward movement of said support over a very short distance and thus form the wall. downstream of the retention zone. This process makes it possible to improve the distribution of the liquid mixture over the width of the conveyor and to reduce, or even eliminate the back and forth movement of the casting head.

This principle is also applied in the method described in French patent 72 76616 according to which a cylindrical bar is used protected by an upper flexible support, for example a strip of paper, which laminates the liquid mixture at the precise point of the cream line, thus creating, by an adjustment appropriate to each production and constantly monitored, a fragile balance between the arrival of liquid and its evacuation in the expansion zone. According to this method, the downstream wall is formed by the cylindrical bar in combination with the line of cream which immediately follows it.

Another known method is described in French patent 71 31528, which consists in distributing the liquid mixture on the conveyor by means of a container or trough, in which the reagents are introduced from the bottom and where their expansion begins to happen. The reactants, in the form of nascent foam, overflow from this container to pour onto the conveyor.

All of these known methods and devices have drawbacks.

In the first three processes mentioned above, the upstream wall is always formed by the bottom of the conveyor which must necessarily be inclined. The main drawback, arising from this design, is the difficulty of controlling the parasitic flow of the liquid phase of the reactants, below the line, of cream.

• a) -la zone de rétention, constituée par un récipient statique est sujette à un encrassement continuel inévitable en raison de la nature évolutive du mélange;
• b)- la capacité du récipient ne pouvant être modifiée en cours de fabrication, la réactivité du mélange doit par conséquent, être lente sans possibilité de l'adapter aux autres impératifs;
• c)- le volume de matière, relativement important, contenu dans le récipient et le fait que la réaction commence à s'y déclencher, sont des facteurs d'élévation progressive de la température dans ledit récipient, ce qui modifie l'évolution de la transformation du mélange réactif;
• d)- les écoulements parasitaires sous la mousse en expansion ne sont pas totalement éliminés en raison de l'utilisation d'un convoyeur incliné.

. The disadvantages of the last process mentioned above are the following:.

• a) -the retention zone, consisting of a static container is subject to inevitable continual fouling due to the evolving nature of the mixture;
• b) - the capacity of the container cannot be modified during manufacture, the reactivity of the mixture must therefore be slow without the possibility of adapting it to other requirements;
• c) - the relatively large volume of material contained in the container and the fact that the reaction begins to start there, are factors of progressive rise in temperature in said container, which modifies the evolution of the transformation of the reactive mixture;
• d) - parasitic flows under the expanding foam are not completely eliminated due to the use of an inclined conveyor.

As has just been exposed, the mixture, during its expansion, progressively passes from the liquid state to the solid state, the finished product being able to be rigid or flexible depending on the degree of crosslinking of the polymer. The rapidly viscous then pasty state of the mixture causes against the walls of the shaper whatever it is: a closed or open mold on top, a retainer which slows down the expansion of the cells coming into contact with the walls.

In the context of the production of blocks or strips of a rectangular cross section in particular, it results from this phenomenon, a rounded shape of the upper face of the foam block at the end of the expansion. This shape is the source of significant material losses during the manufacture of such blocks or strips.

We therefore sought to give the section of continuously cast blocks as rectangular as possible.

A known method and device consists in lining the lateral movable walls with a polyethylene film drawn first at a determined angle to the point of completion of the expansion of the foam, from which, after forming a fold , it then accompanies the foam block until it leaves the conveyor.

According to another method, the foam in formation is compressed using weighted pads bearing on the upper face of the block, by means of a strip of paper or a strip of non-woven fiber, which accompanies the block when moving on the conveyor.

Another process described in French patent 71 31528 consists in placing the pouring point at substantially the same altitude as the upper face of the block to be obtained and the foam is expanded by the controlled inclination of the conveyor.

These three methods have drawbacks.

The drawbacks of the first method lie in the fact that it requires the use of sheets of a very flexible material with a view to its deformability. Such a material, preferably polyethylene, is relatively fragile and currently expensive since it is a petroleum derivative.

On the other hand, the fold formed at the end point of the expansion of the foam leaves traces on the lateral faces of the strips, which make it necessary to straighten the flanks, which results in significant material piercing.

The disadvantages of the second method are first of all that it requires complex apparatus and delicate adjustment. In addition, any variation in the cream line generates air inclusion between the paper strip and the upper face of the block, which then has deep, sometimes significant cracks, which results in the loss of part Of the band. Also according to this process, the upper paper can only be removed after total gelation of the block, that is to say twenty-five to thirty meters after casting and consequently the defects are only visible to the operators from this moment, which causes a considerable delay in corrective maneuvers.

The drawback of the third method lies in the complexity of the device for varying the width of the strip of foam during manufacture.

The rigid foam sheets, of controlled thickness and each side of which is made up of a protective material: paper, fabric, plasterboard, wood, etc. are generally manufactured continuously, in standard width preferably one meter. twenty centimeters, by means of horizontal conveyors known as double belts, one lower of which supports a band which receives the reactive mixture and the other upper comprises a band which limits the expansion of the product and ensures, in addition to sizing, the flatness of the upper side.

In this type of manufacturing, it is useful to be able to adjust the distance between the pour point, or retention zone, and the entry of the mixture being expanded under the upper conveyor. Likewise, it is necessary to control the temperature of the lower flexible support in the part preceding the entry of the mixture into the passage existing between the upper conveyor and the lower conveyor.

• - d'obtenir une zone de rétention délimitée avec précision par les éléments mécaniques du dispositif;
• - de contrôler, faire varier et ajuster le volume de ladite zone selon les caractéristiques du mélange réactif et du produit à fabriquer;
• - d'utiliser à ces fins une combinaison d'éléments ayant entre eux un mouvement relatif continu et dont le sens est déterminé de telle sorte que le mélange en phase liquide soit maintenu dans cette zone, sans fuite appréciable, pour s'écouler ensuite naturellement sur le convoyeur dont l'extrémité amont constitue une paroi de la zone de rétention;
• - de régler les altitudes et mouvements respectifs des appareils de telle sorte que l'écoulement du mélange liquide ne soit possible que dans la direction du convoyeur sans qu'il soit nécessaire d'incliner celui-ci.

An objective of the invention consists in the implementation of means for the manufacture of flexible or rigid polymer strips and allowing:

• - to obtain a retention zone delimited with precision by the mechanical elements of the device;
• - controlling, varying and adjusting the volume of said zone according to the characteristics of the reactive mixture and of the product to be manufactured;
• - to use for these purposes a combination of elements having between them a continuous relative movement and whose direction is determined so that the liquid phase mixture is maintained in this zone, without appreciable leakage, to then flow naturally on the conveyor, the upstream end of which forms a wall of the retention zone;
• - to adjust the respective altitudes and movements of the devices so that the flow of the liquid mixture is only possible in the direction of the conveyor without it being necessary to tilt it.

Another objective of the invention is to produce strips of flexible polymer foam with a rectangular cross section whose upper face is flat.

Another objective of the invention is the manufacture of rigid foam plates loaded and / or lightened, in particular plates having in their thickness longitudinal and parallel channels between them while the currently known techniques only allow the production of solid panels in virgin matter.

These objectives are achieved by the process according to the invention for the production of continuous strips of polymer foam obtained from a mixture of liquid reactants, generators of expanded foam, according to which said mixture of reactants is continuously introduced. . liquid in a container and in that the mixture is allowed to expand at such an outlet that once fully expanded, the foam supported by a U-shaped conveyor, animated in a continuous movement takes the form of a band of rectangular cross section, characterized in that the volume of said container is determined to form a zone of retention of the mixture of reactants in the liquid phase and in that the level of this mixture is maintained at a level slightly higher than the plane over which the mixture flows in the liquid state, so that the primary phase of the expansion of the mixture and its expansion occur outside the container on a surface animated by a continuous movement under the effect of the conveyor, which surface is maintained in a substantially horizontal plane.

The volume of the container is in particular determined by operating over at least its length, so that the retention zone defines the width of the foam strip.

These objectives are also achieved by the device according to the invention for producing strips of polymer foam obtained from a mixture of liquid reactants generating an expanded foam and comprising a container, means for continuously introducing into this container , said mixture of liquid reactants and a U-shaped conveyor, animated by a continuous movement on which the foam is deposited to take the form of a strip of a rectangular cross section, characterized in that the container has a front wall, a rear wall and two side walls, the front and rear walls of which also constitute the bottom of the container and in that the front wall, which is situated on the side of the conveyor, is a curved wall constituted by a cylinder, driven in rotation around a axis substantially horizontal in the same direction and at the same speed as the conveyor and in that the edges of the side walls, located on the side of the curved wall, are of a circular outline and partially surround the cylinder in order to allow the relative movement of the cylinder and of the other walls while ensuring the sealing of the container.

The upper edge of the rear wall and the side walls of the container are located at a level higher than that of the front wall, which tangents a substantially horizontal surface over which the mixture of reactants in liquid phase flows, which horizontal surface is animated. of a continuous movement under the effect of the conveyor.

The assembly: rear wall, side walls, includes means for obtaining its pivoting around the axis of said cylinder in order to raise or lower said assembly relative to said horizontal surface in order to modify the volume of the container. ; and to immobilize in position said assembly after adjustment.

According to one embodiment, the rear wall of the container is a curved wall formed by a cylinder, driven in rotation in the same direction as the front cylinder, which cylinders are mounted on two axes parallel to each other and are substantially tangent, the line of tangency constituting the bottom of the container and in that the side walls are parallel to each other and are above the cylinders and their lower edge is delimited by two concurrent circular lines at a point located in the vicinity of said line of tangency, which side walls partially surround the cylinders in order to allow on the one hand the rotation of the cylinders and on the other hand the relative movement of the rear cylinder / side walls assembly around the front cylinder while ensuring the tightness of the container.

The rear cylinder has a larger diameter than the front cylinder and is rotated at a slower speed than that of said front cylinder.

. The rear cylinder is immersed in a solvent tank and is subjected to the action of a squeegee extending in the longitudinal direction of the cylinder to detach the polymerized particles adhering thereto at its periphery.

Each of the side walls has a counter plate extending from the side of said horizontal surface on which the mixture of reactants in the liquid phase is deposited to seal at the junction of the side walls and said surface, which counter plates are adjustable in position on the walls.

Said side walls include means for bringing them towards one another or away from one another and for immobilizing them in position.

At least one of said cylinders comprises a bundle of conduits which are parallel to each other and to the axis of rotation of the cylinder, in which conduits a coolant is circulated in order to raise or lower the temperature of the cylinder and correspondingly the temperature of the mixture of reactants in liquid phase.

The curved wall formed by said cylinder, located at the front of the container on the side of the conveyor and the rear wall of the container, define a space in which a flexible sheet has passed, which partially wraps around said cylinder on which it moves. in the container, which sheet continues to run while being supported by the conveyor and constitutes said horizontal surface on which the mixture of reactants is deposited.

In one embodiment, the flexible sheet is applied against the lower part of said front cylinder, below. from the bottom of the container, by means of a roller subjected to the action of elastic means.

In another embodiment, the flexible sheet is applied against the lower part of the rear cylinder, below the line of tangency of the two cylinders by means of a roller subjected to the action of elastic means, which sheet is then passed between the two cylinders and partially surrounds the front cylinder from above to extend tangentially thereto in a substantially horizontal position.

In the device according to the invention, the mixture of which is introduced at the source into the container, a characteristic is that it comprises at least one tube passing through each of the walls. lateral, which tubing is slidably mounted to be positioned in the casting head and has along its length openings to ensure the distribution of the mixture in the liquid state in said head.

In a particular embodiment, the tubing consists of several coaxial tubes, arranged in the extension of one another and of tapering section with respect to the circulation of the mixture, so as to reserve between them substantially annular spaces of the same section, which corresponds approximately to the section of the smallest central tube.

The device according to the invention also comprises a substantially horizontal plate, of a width at least equal to that of the conveyor and the upper face of which is tangent to the front cylinder of the container, which tray extends from said front cylinder to. 'to the conveyor and supports the sheet on which the foam develops.

In said device, in which the U-shaped conveyor consists of a mat carrying the flexible sheet on which the foam develops and whose side walls are constituted by two flexible sheets, each from a vertical roller located at the front of the device on the container side, which sheets extend over the length of the conveyor and are wound around a vertical roller situated at the rear of the device, said sheets moving at the speed of the mat while being attached to the side of their lower edge along the lateral edges of said sheet, carried by the conveyor, a characteristic consists in the fact that it furthermore comprises parallel and close to each of the internal faces from the side walls of the conveyor, another inclined flexible sheet, which comes from a roll located on the side of said container, extends over at least the part of the device where the reactants deposited in liquid phase on said horizontal sheet enter into reaction and develop until the total expansion of the foam, which sheet moves in this part in a rectilinear direction from the inlet to the outlet of the device and from the bottom up to be supported by a roller located above of the conveyor, its inclination being such that its lateral edges are substantially parallel to the slope of the mixture in the reaction phase in order to obtain strips of foam having an upper face pla forming with their lateral faces sharp edges free from surface defects.

The inclined parts of said sheet are located above the conveyor and the casting head and one of the parts is inclined up and down and folded along a parallel rectilinear member and adjoining the horizontal sheet and the other part is returned from bottom to top at the same inclination as that of said first part.

In its design for the implementation of rigid foam panels, the device according to the invention, comprising a lower conveyor, carrying a flexible sheet on which the mixture of reactants is deposited and a second conveyor disposed above said conveyor lower and parallel to it and on which. is applied a flexible sheet on the lower strand of the upper mat, which conveyors define a space which determines the thickness of the rigid foam panels, is characterized in that the container in which the liquid reactants are introduced is movable in the longitudinal direction of the device and comprises means for being immobilized in position relative to the conveyors,

In this embodiment, the plate, which extends between the container and the lower conveyor, consists of at least two thin plates, mutually parallel and adjacent, which plates are telescopic to adjust the length of the plate so de-connect the container and the conveyor.

This device comprises, in the space existing between the lower conveyor and the upper conveyor, bars parallel to each other and arranged in the same plane, which bars are cantilevered and are fixed to the structure of the device on the side of said container and extend towards the conveyors, so that their free end, which is located between said conveyors, is located substantially at the place where the solidification of the foam occurs.

Each of these bars is surrounded by a sheath slightly larger than the bar so that it can be moved along the latter under the effect of the foam during its expansion in order to continuously produce and delimit channels in the foam panels.

The invention also relates to a new product consisting of a rigid foam panel whose large faces are covered with sheets of protective material, characterized in that it comprises, in its thickness, parallel channels between them, the peripheral wall is protected by a sheath adhering to the foam.

• -elle est simple de conception et facile à adapter sur tous les types de machines de moussage;
• - elle peut être utilisée aussi bien pour la fabrication de la mousse souple que pour la fabrication de la mousse rigide;
• - elle offre la possibilité de faire varier la laize en continu;
• - également la possibilité de faire varier en continu le volume du liquide en rétention avant le démarrage de la réaction de moussage ou, selon le besoin, la possibilité de conserver ce volume constant tout en changeant de laize : il'n'est donc pas nécessaire de faire un ajustement de catalyse;
• - elle permet de réguler facilement la température des différents constituants de l'appareil, ces températures pouvant elles-mêmes être différentes;
• - elle est basée sur un procédé sain : pas de pistolage, de projection et de formation excessive de vapeurs au point de coulée;
• - elle permet, de contrôler la teneur en air du mélange réac- tif;
• - elle permet d'obtenir une couche de mousse uniforme et régulière sur toute la laize (avantage important pour les plaques de faible épaisseur ou les blocs en continu à section rectangulaire);
• - par suite de l'élimination du problème de la ligne de crème, elle permet des formulations plus simples et également d'utiliser de nouvelles matières premières;
• elle offre la possibilité plus particulièrement pour la mousse rigide d'isolation, d'obtenir des produits composites avec parements rigides : plaques de plâtre, panneaux de bois aggloméré, contre- plaqué, feuilles de métal etc ... sans avoir à utiliser le procédé dit "inverse", qui a le gros inconvénient d'entraîner de lourdes pertes latérales de matière;
• - elle offre la possibilité de laminer sur des supports souples : tissus, papier, films etc ...;
• - par rapport au dispositif à goulotte fixe et à l'exception des flancs mobiles, de surface réduite, il n'y a aucune zone sans mouvement où la mousse peut se figer et nécessiter un décrochage manuel. Le risque d'icebergs est supprimé. Le problème de la propreté de la goulotte,qui est très important pour un écoulement régulier, ne se pose plus avec le dispositif mettant en oeuvre le procédé selon l'invention;
• - l'invention permet en outre une maîtrise plus grande de la vitesse de défilement du convoyeur de coulée. Cette vitesse pouvant être notablement réduite; la longueur des installations peut être diminuée en conséquence, d'où une réduction importante des coûts d'investissements.

The advantages of the invention lie at various levels:

• - it is simple in design and easy to adapt to all types of foaming machines;
• - It can be used both for the manufacture of flexible foam and for the manufacture of rigid foam;
• - it offers the possibility of varying the width continuously;
• - also the possibility of continuously varying the volume of the liquid in retention before the start of the foaming reaction or, if necessary, the possibility of keeping this volume constant while changing the width: it is therefore not necessary to make a catalysis adjustment;
• - It allows to easily regulate the temperature of the various components of the device, these temperatures can themselves be different;
• - it is based on a sound process: no spraying, spraying and excessive formation of vapors at the pouring point;
• - it makes it possible to control the air content of the reactive mixture;
• - it makes it possible to obtain a uniform and regular layer of foam over the entire width (important advantage for the sheets of thin or continuous blocks with rectangular section);
• - following the elimination of the problem of the cream line, it allows simpler formulations and also the use of new raw materials;
• it offers the possibility, more particularly for rigid insulation foam, of obtaining composite products with rigid facing: plasterboard, chipboard panels, plywood, metal sheets, etc. without having to use the process. called "reverse", which has the major drawback of causing heavy lateral losses of material;
• - it offers the possibility of laminating on flexible supports: fabrics, paper, films etc ...;
• - compared to the device with fixed chute and with the exception of the movable sides, of reduced surface, there is no zone without movement where the foam can freeze and require a manual release. The risk of icebergs is eliminated. The problem of the cleanliness of the chute, which is very important for a regular flow, no longer arises with the device implementing the method according to the invention;
• - The invention also allows greater control of the running speed of the casting conveyor. This speed can be significantly reduced; the length of the installations can be reduced accordingly, resulting in a significant reduction in investment costs.

In terms of the production of foam-generating reactants and whatever the method of designing the container according to the invention, the upstream wall of the retention zone, formed either by the rear cylinder or by the wall of the tank, is always at an altitude higher than that of the front cylinder. The downstream wall is formed, at its lower part, by the flexible bottom support conforming to the shape of the front cylinder and at its upper part by the line of cream with this peculiarity that the retained volume of reactive liquid, therefore of the water table. The flow which determines the height of the block can be controlled to a large extent, approximately in a proportion of 1 to 2.

The substantially horizontal position of the conveyor no longer causes parasitic flow of the liquid phase under the expanding phase, a drawback already mentioned on inclined conveyors and which requires a minimum speed. In the proposed method, the speed can be reduced as much as the reactivity of the mixture allows, resulting in a proportional reduction in the length of the installations.

The invention offers the possibility of regulating the temperature of the cylinders or the tank. It being recalled that the foaming reaction generates heat, it is important to be able to maintain the mixture and the equipment at a constant temperature. It is preferable to use a heat transfer fluid passing through the cylinders and capable of removing the calories produced or, on the contrary, providing them if necessary.

Experience having shown that a high temperature (50 to 60 °) of the flexible bottom limits the over-densification of the base of the foam (2 to 3% savings on the material) and that, on the other hand, a low temperature between 17 and 20 ° delayed the distillation of the auxiliary blowing agents (monofluotrichloromethylene) one immediately sees the advantage of cooling the rear cylinder and reheating the front cylinder.

During manufacture, it is possible to vary the width of the foam block by moving the movable sides and, at the same time if necessary, to change the position of the rear cylinder or of the tank to keep the same volume in the retention zone. liquid or modify it.

The arrival of the reactive liquid can be carried out either by runoff on a chute, or at the source by two lateral pipes crossing the movable sides and each constituted by a series of nozzles: concentric with decreasing sections from upstream to downstream, so that the nozzles have all the same section or neighboring sections to avoid any turbulence in the liquid mixture and to ensure the distribution of the mixture in the container.

It is possible to integrate a powdery or granulated, dry or impregnated charge, spread over the rear cylinder using, for example, a hopper and a suitable distributor. The addition of fillers in polyurethane foam, which has always encountered difficulties in conveying them into the mixture, is resolved by this process. This characteristic is especially interesting for the manufacture of rigid foam insulation panels between two facings.

The apparatus as described above can easily be adapted to existing conveyors, in particular for the manufacture of flexible foam, without losing the advantage of the formation of the cream line on a horizontal plane.

This adaptation can be extended to rigid foam production machines, known as "double band" machines, while retaining the option generally offered by these machines, of adjusting the distance between the casting head, here the retention zone, and the inlet. of the double belt conveyor.

• - L'angle de montée peut être réglé à la vue et sans retard;
• - la face supérieure de la bande n'est pas obstruée pendant le dégazage qui marque la fin de l'expansion;
• - la bande se forme en expansion libre sur toute sa largeur;
• - la matière en cours d'élaboration est sous le contrôle visuel permanent des opérateurs.

The method and the device according to the invention also make it possible to obtain flexible foam strips of a rectangular cross section having no deterioration of the sides and having a flat upper face.

• - The angle of climb can be adjusted at sight and without delay;
• - the upper face of the strip is not obstructed during degassing which marks the end of the expansion;
• - the strip is formed in free expansion over its entire width;
• - the material under development is under the permanent visual control of the operators.

The method and the device according to the invention finally allow the manufacture of rigid foam sheets. The adoption of a source-supplied cylinder head, allows placing a device capable of creating longitudinal channels in the thickness of the panel being formed and thus achieving a significant saving of raw material.

• - la figure 1 est une vue en élévation très schématique d'un dispositif selon l'invention pour fabriquer des bandes de mousse de polymères souples et comportant une tête de coulée à cylindres,
• - la figure 2 est une vue en coupe du dispositif de la figure 1 suivant la ligne II II,
• - la figure 3 est une vue en coupe schématique partielle à plus grande échelle de la partie avant du dispositif de la figure 1, illustrant la tête de coulée dans un mode d'exécution et dans sa disposition où la zone de rétention est maximale,
• - la figure 4 est une vue schématique de la tête de coulée de la figure 3 dans sa disposition où la zone de rétention est minimale,
• - la figure 5 est une demi-vue de dessus schématique de la tête de coulée de la figure 3,
• - la figure 6 est une vue en élévation partielle de la partie mécanique du récipient composant la tête de coulée,
• - la figure 7 est une vue de dessus partielle du mécanisme de la figure 6,
• - la figure 8 est une vue en coupe schématique d'une tête de coulée dans un autre mode de réalisation et comportant un seul cylindre. Sur cette figure, le récipient est réglé pour que sa contenance soit maximale;
• - la figure 9 est une vue en coupe schématique de la tête de coulée de la figure 8, dont le récipient est réglé pour que sa contenance soit minimale,
• -la figure 10 est une vue en coupé longitudinale schématique d'un dispositif selon L'invention pour la fabrication de panneaux de mousse de polymère rigide,
• - la figure 11 est une vue en coupe longitudinale schématique de la partie avant du dispositif de la figure 10, comportant des aménagements pour obtenir des panneaux rigides. comportant des canaux longitudinaux,
• - la figure 12 est une vue de dessus d'un des noyaux formateurs desdits canaux et de ses accessoires et qui illustre la mise en oeuvre des gaines des canaux des panneaux rigides selon un mode de réalisation,
• - la figure 13 est une vue en perspective partielle d'un panneau de mousse rigide selon l'invention,
• - la figure 14 est une vue en coupe longitudinale d'un des conduits d'alimentation en source du mélange de réactants dans les récipients à cylindre selon l'invention,
• - la figure 15 est une vue suivant F₁ du conduit de la figure 14.

Others. advantages will also emerge from the following description of various preferred embodiments of the device according to the invention with reference to the appended drawing in which:

• FIG. 1 is a very schematic elevation view of a device according to the invention for manufacturing strips of flexible polymer foam and comprising a casting head with cylinders,
• FIG. 2 is a sectional view of the device in FIG. 1 along line II II,
• FIG. 3 is a partial schematic sectional view on a larger scale of the front part of the device of FIG. 1, illustrating the casting head in an embodiment and in its arrangement where the retention zone is maximum,
• FIG. 4 is a schematic view of the pouring head of FIG. 3 in its arrangement where the retention area is minimal,
• - Figure 5 is a schematic half-view from above of the casting head of Figure 3,
• FIG. 6 is a partial elevation view of the mechanical part of the container making up the casting head,
• FIG. 7 is a partial top view of the mechanism of FIG. 6,
• - Figure 8 is a schematic sectional view of a casting head in another embodiment and comprising a single cylinder. In this figure, the container is adjusted so that its capacity is maximum;
• FIG. 9 is a schematic sectional view of the pouring head of FIG. 8, the container of which is adjusted so that its capacity is minimal,
• FIG. 10 is a schematic longitudinal section view of a device according to the invention for the production of rigid polymer foam panels,
• - Figure 11 is a schematic longitudinal sectional view of the front part of the device of Figure 10, comprising arrangements for obtaining rigid panels. having longitudinal channels,
• FIG. 12 is a top view of one of the forming cores of said channels and of its accessories and which illustrates the use of the sheaths of the channels of the rigid panels according to one embodiment,
• FIG. 13 is a partial perspective view of a rigid foam panel according to the invention,
• FIG. 14 is a view in longitudinal section of one of the supply pipes at the source of the mixture of reactants in the cylinder containers according to the invention,
• - Figure 15 is a view along F ₁ of the conduit of Figure 14.

Reference is first made to FIGS. 1 to 7 of the drawing which illustrate the invention in an embodiment for obtaining strips of flexible polymer foam.

The device of Figure 1 consists of a conveyor 1, extending in a substantially horizontal plap whose supporting strand supports a flexible sheet 2, from a roll 3. This sheet 2, for example of paper is of 'first passed through a casting head 4 and is supported, while being able to slide, on an intermediate plate 5, arranged between the head 4 and the conveyor 1.

The plate 5 and the carrying strand 1a of the conveyor 1 are substantially in the same plane. The side walls of the conveyor 1 are formed in a known manner by flexible sheets 6, from two rollers 7. The rollers 7 are arranged perpendicular to the conveyor 1 and the sheets 6 are adjacent to the side edges of the horizontal sheet 2. L the set of sheets 2/6, forming a corridor of a U-shaped cross section, moves at the speed of the conveyor 1 in the direction of the arrow F. As shown in the drawing, the rollers 7 are for example located at level of the drum before lb of the conveyor 1. We will return later to this figure to complete its description concerning other arrangements relating to the invention.

In one embodiment, the casting head 4 is shown in Figures 3 to 7 of the drawing.

The device in which the liquid phase reactants are introduced with a view to mixing them and ensuring the function of distributor of this liquid mixture is called pouring head before its expansion occurs until the final phase where it takes the consistency of 'a foam.

According to the invention the method consists in determining the volume of a container to form a retention zone for the mixture of reactants in the liquid phase and the level of this mixture is maintained at a level slightly higher than the plane in which the sheet 2 moves. , so that the primary phase of the expansion of the mixture and its expansion takes place outside the container, on said sheet 2, which is moved in the direction of arrow F to bring the mixture in reaction into contact with the walls of the conveyor 1/2/6 which give the foam strip its final shape, this being for example of a rectangular cross section.

Figures 3 to 7 show a preferred embodiment of the casting head, which consists of a container 8 composed of two cylinders of the same length 9/10 and two side walls 11. The cylinders 9/10 are of different diameters, so that the cylinder 9 is smaller than the cylinder 10. These cylinders are parallel to each other and are arranged horizontally and transversely to the conveyor 1. The cylinder 9 is located near the plate 5 and is very close from the other cylinder 10 so as to leave a slight space between them for the passage of a film, for example a sheet of paper 2. In this position, the cylinders are substantially tangent and the line of tangency marked 12 constitutes the lower end part of the container. This comprises two animated curved front / rear walls, which are constituted by said cylinders 9/10 as well as side walls 11 which are arranged above the cylinders, are parallel to each other and extend perpendicular to the generatrices of said cylinders 9 / 10. Their lower edge is formed by two curved lines lla / llb which converge at point llc, which is located in the vicinity of the line of tangency marked 12. Line lla is a circular line of a ryon R ₁ having as its center the axis of rotation of the cylinder 10. This circular line 11a closely circumvents the periphery of the cylinder 10. The line llb is a circular line of. radius R ₂ , having as its center the axis of rotation of the cylinder 9. The circular line 11b bypasses the periphery of the cylinder 9 and is supported on the sheet of paper 2. The curved line 11b is extended by a straight line 11d s' extending above the plate 5. The upper part of the cylinder 9 is substantially tangent to the plane in which the plate 5 is located and in which the flexible sheet 2 moves.

This comes from a roller 3 located below the casting head, which roller is parallel to the cylinders 9/10.

The sheet 2 is first supported on a first roller 3a; mounted to rotate freely on the machine structure and is applied against the cylinder 10 by a roller 3b. The sheet 2, coming from the paper roll 3 first partially bypasses the cylinder 10, passes into the space 12, bypasses the upper part of the cylinder 9 to continue its race horizontally on the plate 5 and the carrying strand 1a of the conveyor 1 .

The set of cylinders 9/10 and side walls 11 is pivotally mounted around the axis of the cylinder 9, so that the volume of the mixture retention zone 8 can vary depending on the angular position of said set. The angular movement a is for example 15 °. At the position illustrated in Figure 3, the cylinder 10, being in its lower extreme position, the volume of the retention zone 8 is maximum. In FIG. 4, the cylinder 10 is in its extreme upper position and the volume of said zone 8 is minimum.

As can be seen in Figure 3; the angle formed between the line 11d of said side walls 11 and the plane in which the sheet 2 moves is the angle a of movement of the container for example 15 °. In order to seal the container between the side walls 11 and the sheet of paper 2, each wall 11 comprises, on the side of the plate 5, a counter plate 13 intended to mask the vacuum existing between the line 11d and the sheet 2 This counter plate 13 has, at its lower part, a circular edge 13a extended by a straight line 13b. The lower edge of the plate 13 thus follows the contour of the upper part of the cylinder 9 and extends over part of the plate 5. The counter plates 13 also have a curved opening 13c to allow their positioning on the side walls 11 and their fixing is ensured for example by means of two bolts 14 or by any other equivalent means.

The cylinders 9/10 are rotated in the direction of the arrows F2 which is also the direction of the conveyor. 1. The cylinder 9 is driven at the speed of the conveyor 1. The cylinder 10 rotates at a slower speed.

The admission of the liquid mixture into the container 8 can be carried out in two ways either by means of a dispensing head 15 which pours the liquid mixture onto a distribution chute 16, situated above the cylinder 10, or by means of two horizontal tubes 17 introducing the source liquid through the side walls of the container. Each of these tubes passes through one of the side walls 11 and brings the mixture of reactants without turbulence into the container.

One embodiment of such tubing 17 is illustrated in Figures 14/15 of the drawing. It consists of several coaxial tubes 17a / 17b / 17c / 17d placed in the extension of each other so that the end of the tube 17e can reach the central area of the casting head whatever the position of the side walls 11 relative to the median axis of the head. This tubing is therefore mounted adjustable in the wall 11 which it passes through and the seal, at the right of passage therein, is obtained for example by means of a lip seal 17f allowing its sliding. Each of the tubes 17b / 17c / 17d reserves in combination with the one in which it is engaged and which it extends 17a / 177b / 17c, an annular space 17g / 17h / 17k substantially of the same section, which approximately corresponds to the section of the most small tube 17d. The positioning of the tubes between them is obtained by means of spacers 17ℓ, distributed around the tubes. The mixed in the liquid state is thus distributed in the casting head at the same flow rate and without turbulence by the annular spaces 17g / 17h / 17k as well as by the central tube 17d.

An embodiment of the supporting structure of the cylinders 9/10 and of the side walls 11 is given with reference to FIGS. 6 and 7.

The cylinders 9/10 are rotated by being mounted on two arms 18 parallel to each other and arranged on either side of the cylinders. The large cylinder 10 is mounted adjustable on the supports 18 in bearings 19 mounted on slides and comprising adjustment means 19a and stop 19b to allow it to move away from or closer to the cylinder 9, and to immobilize it in position .

The cylinder 9 is mounted in a fixed position at one end of the arms 18. The assembly is carried by bearings 20 fixed to the chassis of the machine. In this design, the arms 18 and all of the elements which they carry can pivot around the axis of the cylinder 9, marked 21. The roller 3b, intended to press the sheet of paper against the cylinder 10, is carried by two rods 22, articulated by their middle around an axis 23 carried by a lug extending to the lower part of the arms. The links 22 are subjected to the tension of a spring 24, hooked to the arms 18, so that the roller 3b is pivoted on the side of the cylinder 10.

The arms 18 are interconnected by a crosspiece 25 and have two extensions 26 extending perpendicularly from bottom to top. These two extensions 26 are mutually parallel and carry at their upper part a threaded rod 27, the thread of which is reversed right / left from its middle. This rod 27 is connected by one of its ends to means for driving it in rotation.

It cooperates with two sleeves 29, which each carry an arm 30 extending perpendicularly to the extensions 26. These arms 30 are parallel to the arms 18 and carry, at their free end, connecting rods 31 at the rate of two links per arm, which links form screeds. These links 31 are articulated on the arms 30 and also on the side walls 11 which make up the container. The walls 11 thus guided are automatically placed above and around the cylinders 9/10, so that they achieve, in combination with said cylinders, an retention volume of an acceptable seal.

The angular movement of the assembly is obtained by means of one or more double-acting cylinders 32, preferably hydraulic, articulated on the one hand at 33 at the end of the mobile structure 18/25/26 and secondly at 34 on a yoke 35 fixed to the chassis of the apparatus.

The choice of the volume of the retention zone 8 is obtained by modifying the angle a of the line XX ₁ on which the cylinders 9/10 are and / or by modifying the length of the container by displacement of the side walls 11, by acting on the screw 27. The walls 11, guided in translation by the supports 30, can be brought towards one another or distant from each other symmetrically to the longitudinal axis of the device. The arm 30 is held parallel to the arm 18 by means of a sliding stop 36 indented at 36a which is integral with it and which cooperates with a slide 37 extending transversely to the casting head and which is parallel to the screw 27. This stop 36 extends perpendicularly to arm 30 and below it each arm 30 has a stop.

The adjustment of the spacing of the side walls 11 determines the width of the strip of foam obtained. The liquid reactant mixture contained in the retention zone 8 and the upper level of which is substantially in the plane of the plate 5 or slightly above, is entrained in the liquid state by the flexible sheet 2, so that the expansion and expansion of the foam occur outside the container on the tray 5, the total expansion continuing on the conveyor 1.

In order to keep the container in a good state of cleanliness, the cylinder 10, which constitutes the rear pardi of the container, is partially immersed in a solvent tank 38, disposed at the lower part of the casting head. This tank 38 includes a squeegee 39 extending transversely to the cylinder and held in position at a suitable angle to detach from the wall of the cylinder the particles of polymerized material which could have adhered to it. As can be seen in the drawing, the tank 38 moves with the assembly when the volume of the retention zone 8 is adjusted and its shape is such that no spillage of solvent can occur.

The cylinders 9/10 also comprise conduits 9a / 10a equidistant from the axis of rotation of the cylinders and extending longitudinally, parallel, to said axis of rotation. The cylinders have rotating joints at their ends to seal at these locations. The purpose of these conduits 9a / 10a is to channel a heat-transfer fluid, for example water, for the purpose of heating or cool the cylinders and correspondingly the mixture of reactants. This design is advantageous because, since the foaming reaction generates heat, it is important to maintain the mixture and the equipment at a constant temperature. It allows in particular to control the temperature at various points in the container. For example, the rear cylinder 10 can be cooled while the cylinder 9 can be heated. Experience has in fact shown that a temperature of 50 to 60 ° of the flexible bottom formed by the flexible sheet 2, limits the overdensification of the base of the foam. On the other hand, a low temperature between 17 and 20 ° delayed the distillation of the auxiliary blowing agents, hence the advantage of cooling the rear cylinder 10 and heating the front cylinder 9.

Another embodiment of a casting head according to the invention is illustrated in Figures 8 and 9 of the drawing.

This consists of a cylinder 40 rotated in the direction of movement of the conveyor belt of the conveyor 1 and on which cylinder 40 is applied a sheet of paper 2 from a reel 3. The partial winding of the sheet 2 on the cylinder 40 is obtained by means of a roller 41 extending parallel to said cylinder. As in the previously described device, the flexible sheet 2 is supported by a horizontal plate 5 and is supported by a conveyor also horizontal.

The cylinder 40, covered with the flexible sheet 2, constitutes the front wall of the container into which the mixture of liquid reactants is introduced. The rear and bottom walls of the container and the side walls form an assembly which can pivot around the cylinder 40 while remaining tightly applied by the side walls to the flexible sheet 2. Whatever the angular position of the container, its upper part is always at a level higher than the plane of the plate 5 in which the sheet 2 moves. In addition to the movable wall formed by the cylinder 40, the container consists of a rear wall 42; which partially follows the contour of the cylinder 40 and has at its lower part a "return" 42a, directed towards the side of said cylinder. A space 43 is reserved between the parts 42a and the cylinder, to allow the passage of the flexible sheet 2. The side walls 42b of the container are delimited on the side of the cylinder by a circular line 42bi, which is extended to the upper part of the container by a straight line 42b ₂ . In the position illustrated in the figure 9, this straight line 42b ₂ is applied against the flexible sheet 2, which seals the container at this location where the mixture, in the liquid state, begins its expansion.

In order to seal the container, whatever the angular position of its part constituted by the walls 42 / 42a / 42b, the device comprises, inside the container and against the internal faces of the side walls 42b, against plates 44 which have the function of masking the vacuum existing between the side walls 42b and the flexible sheet 2, as illustrated in particular in FIG. 8 of the drawing. The counter plates 44 have a fixed position relative to the cylinder 40 and include means for being adjusted and fixed at a determined position relative to the side walls 42b of the container. They have a circular edge 44a extended by a straight part 44b, so as to cooperate closely with the flexible sheet 2. They take the form of a curved strip with parallel lateral edges whose width is greater than the maximum space E left in line with the side walls 42b of the container.

Like the pouring head described with reference to FIGS. 3 to 7, the device described in FIGS. 8 and 9 may include a source supply in the side walls 42b of the container or by means of a dispensing head located above the container. . Also the side walls 42b can be brought closer or further apart from one another in order to determine the width of the strip of foam to be obtained.

The temperature of the mixture of liquid reactants contained in the container can be controlled by admitting into the cylinder a heat transfer liquid circulating in longitudinal conduits as has been described with reference to FIG. 3. As in the previous device comprising a head casting with two cylinders, the casting head, shown in Figures 8 and 9, allows the reaction mixture to flow in the liquid state, outside the container, ₄ u right of the tray 5, the extension foam forming on the plate 5 to end on the conveyor 1.

Reference is again made to FIG. 1 of the drawing in which the evolution of the mixture of reactants flowing in the liquid phase at station A and which, entering into reaction, develops progressively along a regular slope is schematically illustrated. adopt at point B the final structure of a strip of foam.

So that the upper face 45 of the strip of foam thus formed is planar and that the upper angles of the strip are substantially right angles, it is necessary to accompany the foam during its evolution between points A and B to avoid that the he first viscous then pasty state of the mixture does not cause against the walls of the shaper a restraint which slows the expansion of the cells in contact with the walls. The problem has been solved according to the invention by placing inside the conveyor and against each of the side walls thereof, constituted by sheets of paper 6, a flexible sheet 46 also made of paper, which is unwound in one direction oblique as shown in Figure 1.

The sheet of paper 46, from a roll 47 located in front of and above the cylinder casting head 4 extends in a vertical plane first in a direction inclined up and down to the sheet 2 carried by the plate 5. The sheet 46 is then folded around a member 1b constituted by a very thick wall, the lower edge lc of which is straight and extends parallel by adjoining said sheet 2, so that the parts 46a and 46b move in parallel planes. The part 46b is thus inclined from bottom to top and is wound around a coil 48 situated above the shaping device for the strips of foam, which is constituted by the horizontal sheet 2 and by the two sheets 6 delimiting the side walls of the conveyor. The inclination of the part 46b is substantially that of the material 49 during development. This is taken care of at post A and is accompanied until the end of the expansion at point B. Part 46a of sheet 46 is located, relative to the U-shaped corridor of the conveyor, behind part 46b which is in contact with the foam. This continues its race in the strip state, being guided by the side sheets 6 until complete gelation.

Referring now to Figure 10 of the drawing which illustrates a device according to the invention for manufacturing rigid foam panels. This consists of a horizontal conveyor belt 50 extending in a horizontal plane above which is disposed a second conveyor 51. The two conveyors 50/51 are parallel to each other and are spaced apart from the another of a distance d which corresponds to the thickness of the plate to be obtained.

The lower strand 51a of the conveyor 51 is covered with a sheet, for example of paper 52 from a reel 53 located in before and above the device.

The cylinder casting head 54, which is of the type described with reference to FIGS. 3 to 7, is mounted on a carriage 55 guided by rails 56. The carrying strand 50a of the lower conveyor 50 is covered by a sheet of paper 57, which from a supply reel is supported on a roller 58 and passed into the casting head 54 partially surrounding the front cylinder 54a of the latter. The distance separating the casting head 54 from the lower conveyor 50 is filled by a plate 59 made up of two telescopic parts 59a / 59b. Each of these parts is constituted by a thin metal plate preferably made of copper or aluminum, which are adjacent and superimposed so as to be able to slide relative to each other according to the position of the casting head 54 by report to the conveyors. The length of the plate 59 can thus be modified in a proportion close to 1 to 2 in order to determine a zone of expansion of the mixture and to control its expansion, the heating being ensured by a battery of transmitters with infrared 60 in position. adjustable and whose distribution is determined by the chosen zone length.

The adoption of a cylinder head according to the invention, supplied from a source, which suppresses the arrival of the reactive mixture from the upper part of the device, made it possible to design a device capable of creating longitudinal channels in the thickness of the panels being formed and a significant saving of raw material.

A device of such a design is illustrated in Figures 11 and 12 of the drawing.

Above the casting head 54 and the expansion zone 59, bars 61, preferably cylindrical, are arranged parallel to the direction of movement of the conveyors 50/51. These bars are of a section less than 1 'thickness of the panels and extend horizontally in the middle of the space d existing between the conveyors 50/51. The device comprises several bars 61 parallel to each other, which are located in the same plane. The bars 61 are fixed to the structure of the machine to supports 62, situated at one of their ends and extending in a cantilever above the casting head 54 and between said conveyors 50/51 of such so their. free end is located substantially at the point where the foam takes its consistency. Said bars constitute the cores around which sheaths 63 are formed, obtained from strips of paper 64 or polyethylene film for example, continuously folded by means of conical forming rollers 65 according to a known principle.

Upstream of each bar 61, is disposed a roller 66 on which the sheet 64 is supported from below. The roller 66 is arranged so that the sheet comes to tangent the bar 61 at its lower part. This is of a reduced section and profiled at its part 61a to accompany the sheet 64 before it is brought into contact with the forming rollers 65. These are arranged so as to bring one of the edges of the sheet into overlap on the other, as illustrated in FIG. 12. The sheath thus formed at the level of station A is closed by gluing or by welding by means of two knobs 67 which apply the edges to each other. The sheaths are driven at the same speed as the conveyors 50/51 initially by means of a clamping device and then by the material itself by adhesion of the latter to the sheaths. The foam in formation develops around the sheaths 63 between the conveyors 50/51 until total expansion

The panel obtained at the outlet of the conveyors comprises parallel longitudinal channels between them and delimited by said sheaths. A panel thus obtained is illustrated in Figure 13 of the drawing. The layer of foam 68 calibrated in thickness between the two conveyors 50/51 is protected on the large faces of the panel by sheets of paper 52/57. The channels 69 formed by the cores 61 adopt the shape of the latter and extend in the longitudinal direction of the panel.

In FIG. 13, the example shown comprises channels 69 of a circular cross section, the peripheral wall of which is delimited and protected by the sheaths 63 which adhere to the foam. It should be noted that the sheaths-63 can also be constituted by rigid tubes made of cardboard or plastic.

To obtain panels comprising such rigid sheaths, these are successively routed around the cores 61. The sheaths are split along a generator and are successively routed to be engaged at the end 61a of the cores 61 and are then, as described above, driven by adhesion of the product in formation conveyed by the conveyor.

Claims (21)

1. Method for manufacturing continuous strips of polymer foam obtained from a mixture of liquid reactants, generator of expanded foam, according to which said mixture of liquid reactants is continuously introduced into a container and in that leaves this mixture to expand so that once fully expanded, the foam supported by a U-shaped conveyor, animated in a continuous movement, takes the form of a strip of a rectangular cross section, characterized in that that the volume of said container is determined to form a retention zone for the mixture of reactants in the liquid phase and that the level of this mixture is controlled to a level slightly higher than the plane over which the mixture flows liquid state, so that the primary phase of the expansion of the mixture and its expansion occur outside the container on a surface animated by a continuous movement under the effect of the conveyor, which surface is maintained in a plane h horizontal. 2. Device for producing strips of polymer foam obtained from a mixture of liquid reactants generating an expanded foam and comprising a container (8/42), means (15/17) for continuously introducing into this container, said mixture of liquid reactants and a U-shaped conveyor (1/2/6) animated in a continuous movement on which the foam is deposited to adopt the shape of a strip of a rectangular cross section, the container of which comprises a front wall (9/40), a rear wall (10/42) and two side walls (11 / 42b) characterized in that the front (9/40) and rear (10/42) walls also constitute the bottom of the container and in that the front wall, which is located on the side of the conveyor (1/2/6) is a curved wall constituted by a cylinder (9/40) animated in rotation about a horizontal axis in the same direction and at the same speed as the conveyor (1/2/6) and in that the edges (11b / 42b ₁ ) of the side walls (11 / 42b) located on the side of the courtyard wall be have a circular outline and partially surround the cylinder (9/40) in order to allow the relative movement of the cylinder (9/40) and the other walls (10 / 42142a / 42b) while ensuring the tightness of the container. 3. Device according to claim 2, the upper edge of the rear wall (10/42) and the side walls (11 / 42b) of the container are located at a level higher than that of the front wall (9/40), characterized in that said front wall (9/40) tangents a horizontal surface (2) on which the liquid reactant mixture flows, which horizontal surface (2) is animated by a continuous movement under the effect of the conveyor (1/2/6). 4. Device according to any one of claims 2 and 3, characterized in that the rear wall assembly (10/42), side walls (11 / 42b) comprises means for obtaining its pivoting around the axis of said cylinder (9/40) for the purpose of raising or lowering said assembly (10/42/11 / 42b) relative to said horizontal surface (2) in order to modify the volume of the container, and to immobilize said assembly in position after adjustment. 5. Device according to any one of claims 2 to 4, characterized in that the rear wall of the container (8) is a curved wall constituted by a cylinder (10) driven in rotation in the same direction as the front cylinder (9 ), which cylinders (9/10) are mounted on two parallel axes. between them and are substantially tangent, the line of tangency (12) constituting the bottom of the container (8) and in that the side walls (11) are parallel between them and are above the cylinders (9/10) and their lower edge is delimited by two circular lines (11a / 11b) intersecting at a point (11c) located in the vicinity of said tangency line (12), which walls side partially surround the cylinders (9/10) to allow on the one hand the rotation of the cylinders and on the other hand the relative movement of the rear cylinder (10) / side walls (11) around the front cylinder (9 ) while ensuring the tightness of the container (8). 6. Device according to claim 5, characterized in that the rear cylinder (10) is of a larger diameter than the front cylinder (9) and is rotated at a speed slower than that of said cylinder (9). 7. Device according to any one of claims 5 and 6, characterized in that the rear cylinder (10) is immersed in a solvent tank (38) and is subjected to the action of a squeegee (39) s' extending in the longitudinal direction of the cylinder (10) to detach the polymerized particles adhering thereto at its periphery. 8. Device according to any one of claims 2 to 7, characterized in that each of the side walls (11 / 42b) comprises a counter plate (13/44) extending from the side of said horizontal surface (2) on which is deposited the liquid phase reactant mixture to seal at the junction of the side walls (11 / 42b) and said surface (2), which counter plates (13/44) are adjustable in position on the walls (11 / 42b). 9. Device according to any one of claims 2 to 8, characterized in that at least one of said cylinders (9/10) comprises a bundle of conduits (9a / l0a) parallel to each other and to the axis of rotation of the cylinder, in which conduits (9a / 10a) is circulated a heat transfer fluid to raise or lower the temperature of the cylinder (9/10) and correspondingly the temperature of the mixture of reactants in liquid phase. 10. Device according to any one of claims 2 to 9, characterized in that the curved wall, constituted by said cylinder (9/40) located at the front of the container on the side of the conveyor (1, 2, 6) and the rear wall (10/42) of the container, define a space (12/43) in which a flexible sheet (2) has passed, which partially wraps around said cylinder (9/40) on which it moves in the container, which sheet (2) continues to run while being supported by the conveyor (1,2,6) and constitutes said horizontal surface (2) on which the mixture of reactants is deposited. 11. Device according to claim 10, characterized in that the flexible sheet (2) is applied against the lower part of said cylinder (40) below the bottom of the container by means of a roller (41) subjected to the action elastic means. 12. Device according to any one of claims 2 to 10, characterized in that the flexible sheet (2) is applied against the lower part of the rear cylinder (10) below the line of tangency (12) of the two cylinders (9/10) by means of a roller (3b) subjected to the action of elastic means, which sheet is then passed between the two cylinders (9/10) and partially surrounds the front cylinder (9) from above to extend tangentially thereto in a substantially horizontal position. 13. Device according to any one of claims 2 to 12, the mixture of which is introduced at source into the container (8), characterized in that it comprises at least one tube (17) passing through each of the walls (11 / 42b ), which tubing is slidably mounted to be positioned in the casting head (4) and has along its length openings' to ensure the distribution of the mixture in the liquid state in the casting head. 14. Device according to claim 13, characterized in that that the tubing (17) consists of several coaxial tubes (17a / 17b / 17c / 17d) arranged in the extension of one another and of decreasing section with respect to the circulation of the mixture, so as to reserve between them annular spaces (17g / 17h / 17k) substantially of the same section, which corresponds approximately to the section of the smallest central tube (17d). 15. Device according to any one of claims 2 to 14, in which the U-shaped conveyor consists of a mat (la) carrying the flexible sheet (2), on which the foam develops and whose side walls ( 6) consist of two flexible sheets, each from a vertical roller (7) located at the front of the device on the side of the container (4), which sheets (6) extend over the length of the conveyor (I) and wrap around another vertical roller located at the rear of the device, which sheets (6) moving at the speed of the carpet (la) being joined against the side of their lower edge along the side edges of said sheet (2), carried by the conveyor, characterized in that it further comprises, parallel to and near each of the internal faces of the lateral walls (6) of the conveyor (1), another inclined flexible sheet (46) which comes from a roller (47) located on the side of said container (4) extends over at least the part of the device o where the reactants deposited in the liquid phase on said horizontal sheet (2) enter into reaction and develop until the total expansion of the foam, which sheet moves in this part (46b) in a rectilinear direction from the inlet to the output of the device and from bottom to top to be supported by the roller (48) located above the conveyor (1), its inclination being such that its lateral edges are substantially parallel to the slope (49) of the mixture in reaction phase in order to obtain strips of foam having a flat upper face forming with their lateral faces sharp edges free from surface defects. 16. Device according to claim 15, characterized in that the parts (46a / 46b) of the sheet (46) are located above the conveyor (1) and the casting head (4) and in that the part (46a) is inclined from top to bottom and is folded along a parallel rectilinear member and adjoining the horizontal sheet (2) and the part (46b) is returned from bottom to top according to the same inclination as that of the part (46a). 17. Device according to any one of claims 2 to 14 for the manufacture of rigid foam panels and comprising a lower conveyor (50) carrying a flexible sheet (57) on which is deposited the mixture of reactants and a second conveyor (51) disposed above said lower conveyor ( 50) and parallel to it and on which a flexible sheet (52) is applied to the lower strand of the upper belt (51a), which conveyors (50/51) define a space d which determines the thickness of the foam panels rigid, characterized in that the container (54) into which the liquid reactants are introduced is movable in the longitudinal direction of the device and comprises means for being immobilized in position relative to the conveyor (50). 18. Device according to claim 17, characterized in that the plate (59) which extends between the container (54) and the lower conveyor (50) consists of at least two thin plates (59a / 59b) , mutually parallel and adjacent, which plates are telescopic to adjust the length of the plate (59) in order to connect the container (54) and the conveyor (50). 19. Device according to any one of claims 2 to 14 and 17 and 18, characterized in that it comprises, in the space existing between the lower conveyor (50) and the upper conveyor (51); bars (61) parallel to each other and arranged in the same plane, which bars (61) are cantilevered and are fixed to the structure of the device on the side of said container (54) and extend towards the conveyors (50 / 51) 'so that their free end which is between said conveyors (50/51) is located substantially at the edge where the solidification of the foam occurs. 20. Device according to claim 19, characterized in that each of the bars (61) is enveloped by a sheath (63) slightly larger than the bar, so that it can be moved along the latter under the effect of the foam during its expansion, in order to continuously produce and delimit channels (69) in the foam panels (68). 21. New product consisting of a rigid foam panel (68) whose large faces (52/57) are covered with sheets of a protective material, characterized in that it has in its thickness parallel channels (69) between them, the peripheral wall of which is protected by a sheath (63) adhering to the foam.

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